Thank you!! Again, I apologize for the beginner questions:
What would cause the need for an additional external Amp for the front and center speakers? Is that something dictated by specific speakers or the room/user preference? Also, would that feature be important enough to upgrade the receiver to a higher model? [665 or 765]
Thanks!
j
The size room you mentioned is fairly small and the 465 will work fine. If your friend is concerned about cost, I would stick with the 465; you should not need an external amp.
There are three main reasons an external amp is needed:
(1)
Room Size. larger room - speakers tend to be at higher volume that can tax the receiver output. As mentioned by a previous poster you don't want to run at full volume, to provide some head room for large frequency swings
(2)
Speaker Impedance. While the impedance of a speaker varies with frequency most speakers have a nominal impedence rating usually 8ohms. Some speakers are 6 ohms and some very expensive speakers are 4 ohms or even 2 ohms. The nominal ohm rating of a speaker affects directly the power required. Power equals voltage times current and current is voltage divided by resistance so P= V^2/R. Simplyfying 4 ohms requires twice the power that 8 ohms does. Many 4 ohm speakers require an external amp.
(3)
Speaker efficiency or sensitivity. This is how well the speaker converts power to sound loudness and is measured in dBs. A low effiecieny speaker ( 80 dB or less) requires a lot of power. Most speakers are medium effciency in the randge of 88-90 dB and require average amount of power. High efficiency speakers are those approaching 100 dB and require very little power to create loud sound.
Good luck and have a pleasant day!
Forest Man